To my ears, Ayu's "Will" instrumental always sounded like DJ Shadow's "Mongrel" (2002), but with a different key...
https://www.youtube.com/watch?v=8vEnj79TrFE
I remember back in the day, there was this TV commercial airing non-stop on french TV with DJ Shadow's song, so when Will leaked in 2005 prior to the single release, I was like "Wait a minute..."
(I don't mind if some don't hear the similarities between these two tracks)